It surely took them long enough, Twitch.tv has added 1080p/60fps streaming capabilities to their service by increasing the allowed ingest bitrate to 6000 kbps. This will allow for much more fluid video playback on channels where it has been enabled.
Those channels will have lower bitrate options also! It is coming to all of Twitch in the coming weeks, but for now they are rolling it out slowly to a few channels. To test and see if your channel supports the new higher bitrate formats, visit Twitch Inspector and see if your channel supports "Transcode V2." If so then you're ready to test the higher bitrates and increased quality streams
